1. Technical Field
The present invention relates to a motor provided with a rotor having a rotor magnet arranged at the periphery thereof, the motor being configured so that an importance is attached to the airtightness and heat dissipating properties.
2. Background Art
As the motor of this type, for example, a stepping motor described in Patent Document 1 has been known. This stepping motor is constructed so that a rotor to which a rotor magnet is fixed is provided on the outer peripheral surface of a support shaft portion, and the rotor is rotatably supported on the outer peripheral surface of the support shaft portion by a roller bearing. Also, the whole of the motor is covered with a resin to hold the airtightness.
However, in the above-described conventional stepping motor, since the support shaft portion of the rotor is supported by the roller bearing, a space region occupied by the roller bearing is large, which presents a problem in making the motor small in size. Also, the covering of the whole of the motor with a resin causes a hindrance to the miniaturization of motor.
Further, in the above-described conventional stepping motor, since the whole of the motor is covered with a resin having high heat insulating properties, the heat dissipating properties deteriorate, which also presents a problem in that the durability is decreased by a rise in temperature in the motor. Especially in the case of a stepping motor, since the position of an output shaft is also controlled by maintaining the energization a coil, the interior of motor is liable to become hot. Therefore, the heat dissipating properties must be improved.
[Patent Document] Japanese Patent Publication No. 8-28958